In the petroleum industry, it is necessary to fracture subterranean reservoirs. As those of ordinary skill in the art will appreciate, the subterranean reservoir may require fracturing in order to increase the permeability of the subterranean reservoir. In general, fracturing agents are spherical particles. Sand has been used as a prior art fracturing agents. Sand has a generally spherical shape, has a significant compressibility (i.e. difficult to crush), and is heat resistant.
Nevertheless, as those of ordinary skill in the art will appreciate, the uniformity of sand geometry can vary significantly. A uniform sand particle allows for a high flow rates; therefore, as the uniformity of the sand grain decreases, so does the permeability of the sand, which in turn negatively impacts other characteristics of the fracturing agent.
Items of many shapes, sizes and weights can be injected molded. Prior art devices and methods of injecting fluid plastic to mold articles are known in the art. For instance, see U.S. Pat. No. 7,007,445 entitled “Method of Making A Plurality of Interconnected Vials”, which is incorporated herein by express reference.
However, prior art injection techniques have limited the ability of mold designers to manufacture proppants of suitable size and weight to be used in down hole applications including but not limited to fracturing and gravel packing of wells. For instance, prior art techniques do not allow for the production of spheres in significant quantities. Therefore, an object of the present invention is to manufacture proppants with uniform properties including concentricity, weight, and size. In other words, the manufactured proppants will all have the same properties which include uniform concentricity, weight, compressibility, specific gravity, heat resistance and size. Another object is that the proppants can be molded in large quantities. These objects as well as many others will become apparent from the following description.